[Arm-netbook] HDMI v1.4 Audio Return and Ethernet channels

[Richard Wilbur]

On Mon, Jul 31, 2017 at 11:13 PM, Luke Kenneth Casson Leighton
<lkcl at lkcl.net> wrote:
>  CEC etc i believe is supported i can't remember the details, it's
> covered by the processor and is somewhere in the datasheet.  certainly
> i know there's an hdmi audio kernel module for sound playback in the
> sunxi-3.4 kernel.

Sorry, I explain things well enough.  Sound playback normally refers
to sound output from the kernel to D/A, amplifier, and speakers.  Same
direction as video playback: from computer to monitor.

CEC:  Consumer Electronics Control
Allows devices to pass control information around.  Say you have a
remote control for your television that has "Play" and "Pause" buttons
on it, for instance.  Through CEC the commands could be sent from your
television to the EOMA68-A20 card via the HDMI cable and software
there could respond appropriately to the events.

ARC:  Audio Return Channel
The Audio Return Channel supports sending digital multi-channel sound
upstream (for input to the computer).  This would allow recording,
mixing, special effects, etc.

>  so *i'm* not quotes considering it quotes - if it's there and there's
> a linux kernel module it's there, people can compile it and use it.

>From the sound of things, CEC was there from the beginning and ARC is
new in v1.4 but doesn't require circuit changes on the HDMI
transmitter PCB to accommodate.  ARC does require support in the HDMI
block/subsystem of the SoC.

On the other hand, if we plan to support HEC (HDMI Ethernet Channel)
it requires us to route one more pair of signals as a differential
pair.